The Homogeneity of Interstellar Krypton in the Galactic Disk

Abstract

We present an analysis of high resolution HST Space Telescope Imaging Spectrograph (STIS) observations of Kr I 1236 Angstrom absorption in seven sight lines that probe a variety of interstellar environments. In combination with krypton and hydrogen column densities derived from current and archival STIS and Far-Ultraviolet Spectroscopic Explorer data, the number of sight lines with reliable Kr/H ISM abundance ratios has been increased by 50% to 26--including paths that sample a range of nearly 5 orders of magnitude in f(H_2), over 2 orders of magnitude in <n_H>, and extending up to 4.8 kpc in length. For sight lines contained entirely within the local spiral arm (the Orion Spur), the spread of Kr/H ratios about the mean of log_10[N(Kr)/N(H)]_ISM = -9.02+/-0.02 is remarkably tight (0.06 dex), less than the typical datapoint uncertainty. Intriguingly, the only two sight lines that extend through neighboring structures, in particular gas associated with the Carina/Sagittarius Arm, exhibit relatively large, near-solar krypton abundances (log_10[N(Kr)/N(H)]_combined = -8.75+0.09_-0.11). Although these deviations are only measured at the 2 sigma level, they suggest the possibility that krypton abundances beyond the Orion Spur may differ from the local value.

15 page, including 3 figures and 2 tables, accepted for publication in ApJ

References in corpus (5)

• The Definitive Abundance of Interstellar Oxygen
• The Distribution Of Heavy Elements In Spiral And Elliptical Galaxies
• Mixing Time Scales in a Supernova-Driven Interstellar Medium
• The Abundance of Interstellar Nitrogen
• Background and Scattered Light Subtraction in the High-Resolution Echelle Modes of the Space Telescope Imaging Spectrograph

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• The Impact of Recent Advances in Laboratory Astrophysics on our Understanding of the Cosmos
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• Interstellar Iron and Silicon Depletions in Translucent Sight Lines
• The Interstellar N/O Abundance Ratio: Evidence for Local Infall?
• Interstellar Krypton Abundances: The Detection of Kiloparsec-scale Differences in Galactic Nucleosynthetic History
• Abundances and Depletions of Neutron-Capture Elements in the Interstellar Medium
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• A Closer Look at Some Gas-Phase Depletions in the ISM: Trends for O, Ge, and Kr vs. $F_{\ast }$, $f({\mathrm{H}}_2)$, and Starlight Intensity
• Interstellar Extinction and Elemental Abundances: Individual Sight Lines
• The Interstellar Rubidium Isotope Ratio toward Rho Ophiuchi A
• Rubidium in the Interstellar Medium